Golf club and method of manufacturing the golf club

ABSTRACT

A golf club according to the present invention comprises a face portion ( 1 ) and a neck portion ( 2 ), and metal flow lines ( 3 ) continue from the face portion ( 1 ) to the neck portion ( 2 ). These metal flow lines ( 3 ) extend in a single direction on the face portion ( 1 ). A method of manufacturing a golf club according to the present invention comprises steps of bending a rod member subjected to drawing plastic working on an end and forging the rod member after the bending for integrally molding a face portion ( 1 ) and a neck portion ( 2 ).

TECHNICAL FIELD

The present invention relates to a golf club and a method ofmanufacturing the same, and more specifically, it relates to a structureof a golf club head formed by integrally forming a face portion and aneck portion and a method of manufacturing the same.

BACKGROUND TECHNIQUE

The head part of a golf club includes a face portion having a strokingsurface and a neck portion connecting this face portion with a shaft.While the face portion and the neck portion are integrally formed in agolf club head manufactured by forging in general, the neck portion isso readily deformed in stroking that the neck portion must be thickenedand it is difficult to reduce mass distribution to the neck portion.Further, the face portion and the neck portion are formed in differentsteps respectively and thereafter connected with each other. Therefore,strength on the connected parts of the face portion and the neck portionis disadvantageously reduced.

To this end, the inventors have made deep study on the reason therefor,to recognize that metal flow lines discontinue on the aforementionedconnected parts. They have further investigated metal flow lines invarious conventional products, to find those shown in FIGS. 20 to 24. Ina golf club head shown in these figures, metal flow lines 3 partiallycontinue on connected parts of a face portion 1 and a neck portion 2,and hence it is inferable that strength on the connected parts improves.

Also in this example, however, the metal flow lines 3 are toward variousdirections on the face portion 1 as shown in FIG. 21, and getinhomogeneous on the face portion 1. Therefore, hardness of the faceportion 1 gets so inhomogeneous as shown in FIG. 25 that strength varieswith portions of the face and the thickness of the face must be designedin response to a portion inferior in strength and disadvantageously hardto reduce.

DISCLOSURE OF THE INVENTION

The present invention has been proposed in order to solve theaforementioned problem. An object of the present invention is provide agolf club having a wide sweet spot by rendering metal flow linescontinuously extend over a neck portion and a face portion and renderingthe metal flow lines extend in a single direction on the face portionthereby homogenizing hardness of the face portion while improvingstrength on the aforementioned connected parts and reducing thethickness of the face or reducing the diameter of the neck for applyingresidual mass thereof to a portion around the head.

The golf club according to the present invention comprises a faceportion having a stroking surface (ball hitting surface) and a neckportion connecting the face portion with a shaft, and metal flow lines(grain flows) continue from the neck portion to the face portion whilethe metal flow lines extend in a single direction on the face portion.

The metal flow lines thus continue from the neck portion to the faceportion, whereby strength on the connected parts of the neck portion andthe face portion can be improved. Further, the metal flow lines extendin a single direction on the face portion, whereby hardness of the faceportion can be homogenized.

The aforementioned metal flow lines preferably extend in theaforementioned single direction on the stroking surface. Further, themetal flow lines preferably extend along a plane parallel to thestroking surface. In addition, the metal flow lines preferably extendfrom the neck portion in a direction toward a toe of the face portion.

The difference between the maximum value and the minimum value ofVickers hardness ((Hv) with a load of 2 kg) on a stroking portion of theaforementioned face portion is preferably not more than 30. Vickershardness on the stroking portion is preferably at least 130 and not morethan 160. More preferably, Vickers hardness on the stroking portion isat least 140 and not more than 160. The stroking portion refers to asurface portion of the face portion reaching a prescribed depth from thestroking surface, which is a portion planned to stroke from the first.

The golf club according to the present invention comprises a faceportion and a neck portion integrally formed by bending a rod memberreduced in sectional area by drawing plastic working and thereafterforging the rod member.

The inventors have recognized that a golf club manufactured by theaforementioned method attains the aforementioned excellent effect.

A method of manufacturing a golf club according to the present inventioncomprises the following steps: A rod member reduced in sectional area bydrawing plastic working is subjected to bending. After this bending, therod member is subjected to forging for integrally forming a face portionand a neck portion.

Metal flow line density of a portion for defining the neck portion canbe improved in the rod member, for example, by performing drawingplastic working in the aforementioned manner. The rod member can be bentwhile keeping the metal flow lines effective by performing bending onthe rod member in this state. The face portion and the neck portion canbe integrally formed while keeping the metal flow lines effective to themaximum by forging the bent rod member.

The aforementioned drawing plastic working is preferably performed toplastically work a first end of the rod member to be smaller insectional area than a second end while increasing metal flow linedensity on the first end of the rod member. The aforementioned drawingplastic working may be performed by rolling an end of the rod member,for example.

The aforementioned forging step preferably includes a first forging stepof performing rough forging on the rod member a plurality of times forapproximating the shape of the rod member to a final shape whileensuring metal flow lines and a second forging step of performingprecision forging on a material obtained after the rough forging forworking the material into the final shape. Thus, forging can beperformed while keeping the metal flow lines effective.

The neck portion is formed on a first end of the rod member subjected todrawing plastic working, and the face portion is formed on a second endof the rod member.

BRIEF DESCRIPTION OF THE DRAWINGS

The file of this patent contains at least one drawing executed in color.Copies of this patent with color drawing(s) will be provided by thePatent and Trademark Office upon request and payment of the necessaryfee.

FIG. 1 is a sectional view of a golf club head according to the presentinvention along a direction perpendicular to a stroking surface.

FIG. 2 is a sectional view of the golf club head according to thepresent invention along a direction parallel to the stroking surface.

FIG. 3 is a photograph showing a sectional structure of the golf clubhead according to the present invention along the direction parallel tothe stroking surface.

FIG. 4 is a photograph showing a sectional structure of a neck portionin the golf club head according to the present invention.

FIG. 5 is a photograph showing a sectional structure of a face portionin the golf club head according to the present invention.

FIG. 6A is a diagram showing hardness measuring positions on the faceportion of the golf club head according to the present invention.

FIG. 6B is a diagram showing hardness measurement results on the faceportion of the golf club head according to the present invention.

FIG. 7A is a diagram showing hardness measuring positions on the neckportion of the golf club head according to the present invention.

FIG. 7B is a diagram showing hardness measurement results on the neckportion of the golf club head according to the present invention.

FIGS. 8 to 13B are diagrams showing first to sixth steps ofmanufacturing a golf club according to the present invention.

FIGS. 14 to 19 are sectional views of a material in the respectivemanufacturing steps according to the present invention.

FIG. 20 is a sectional view of a conventional golf club head along adirection perpendicular to a stroking surface.

FIG. 21 is a sectional view of the conventional golf club head along adirection parallel to the stroking surface.

FIG. 22 is a photograph showing a sectional structure of theconventional golf club head along the direction parallel to the strokingsurface.

FIG. 23 is a photograph showing a sectional structure of a neck portionin the conventional golf club head.

FIG. 24 is a photograph showing a sectional structure of a face portionin the conventional golf club head.

FIG. 25 illustrates hardness measurement results on the face portion ofthe conventional golf club head.

FIG. 26 illustrates hardness measurement results on the neck portion ofthe conventional golf club head.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is now described with referenceto FIGS. 1 to 19.

FIGS. 1 and 2 are sectional views of a head portion in a golf clubaccording to the present invention. FIGS. 3 to 5 are photographs showinga sectional structure of the aforementioned head portion.

As shown in FIGS. 1 to 5, the golf club according to the presentinvention comprises a face portion 1 having a stroking surface and aneck portion 2 connecting this face portion 1 with a shaft. Metal flowlines 3 continue from the neck portion 2 to the face portion 1, and amajority of these metal flow lines 3 extend in a single direction on theface portion 1. More specifically, most parts of the metal flow lines 3continuously extend from the neck portion 2 toward a toe 4 of the faceportion 1.

The metal flow lines 3 continue from the neck portion 2 to the faceportion 1 as described above, whereby strength on the connected parts ofthe face portion 1 and the neck portion 2 can be improved. In addition,the majority of metal flow lines 3 extend in the aforementioned singledirection on the face portion 1, whereby hardness on the face portion 1can be substantially homogenized.

In order to confirm such an effect, the inventors have compared Vickershardness ((Hv) with a load of 2 kg) on stroking portions of the faceportions 1 in the inventive and conventional golf clubs. Morespecifically, they have compared Vickers hardness on cutting planes inthe case of cutting the face portions 1 along planes substantiallyparallel to the stroking surfaces. FIG. 6B, Table 1, FIG. 25 and Table 2show the results. FIG. 6A shows Vickers hardness measuring positions.

TABLE 1 Invention: Vickers Hardness of Face Portion A B C D E F G 1 142129 153 147 140 141 133 2 144 140 145 146 141 143 144 3 148 140 149 142143 139 148 4 147 140 147 151 147 151 144 5 143 149 156 152 141 139 1486 151 148 149 148 142 149 158 7 149 147 151 147 142 147 146

TABLE 2 Prior Art: Vickers Hardness of Face Portion A B C D E F G 1 138142 164 157 171 176 177 2 143 135 151 146 167 173 172 3 157 143 133 155150 160 170 4 159 136 138 132 142 149 155 5 143 139 136 135 138 149 1416 138 143 135 141 137 134 141 7 135 132 135

While Vickers hardness is substantially homogeneous in the range ofabout 130 to about 160 (about 140 to about 160 at the center of the faceposition 1) in the present invention as shown in FIG. 6B and Table 1, itis understood that dispersion of Vickers hardness in the prior art islarger than that in the present invention as shown in FIG. 25 and Table2.

In other words, it is understood that hardness on the stroking portionof the face portion 1 is more inhomogeneous in the prior art as comparedwith the present invention. This is inferably because the metal flowlines 3 on the face portion 1 of the prior art are inhomogeneous.

The sizes of respective crystals were regular when observing the crystalstructure of the face portion 1 while the respective crystals weretoward various directions when investigating crystal orientations of therespective crystals, and it has been confirmed that the face portion 1has homogeneous composition as a result.

Hardness was measured also on the neck portions 2 of the golf clubs, andthe results are now described. FIG. 7B and Table 3 show Vickers hardnessmeasurement results on the neck portion 2 of the inventive golf club.FIG. 26 and Table 4 show Vickers hardness measurement results on theneck portion 2 of the conventional golf club. The measurement resultsshown in these figures and tables are results on positions shown in FIG.7A.

TABLE 3 Invention: Vickers Hardness of Neck Portion A B C 1 149 143 1442 151 129 164 3 147 141 159 4 128 131 159 5 161 146 150 6 160 146 154

TABLE 4 Prior Art: Vickers Hardness of Neck Portion A B C 1 148 176 1382 152 165 138 3 164 164 141 4 165 160 142 5 151 157 149 6 157 155 150

As shown in the aforementioned FIG. 7B, Table 3, FIG. 26 and Table 4, itis understood that the hardness of the neck portion 2 of the inventivegolf club is slightly higher than the hardness of the face portion 1 ofthe inventive golf club although slightly lower than the prior art. Thisis inferably because a portion for defining the neck portion 2 wasrolled in a material for improving the density of the metal flow lines 3as described later.

Referring again to FIG. 1, a majority of metal flow lines 3 continuouslyextend in a single direction (the direction from the neck portion 2toward the toe 4) at least on the stroking surface of the face portion 1and in the vicinity thereof. In other words, the majority of metal flowlines 3 extend in the aforementioned single direction in a layeredmanner along the smoking surface of the face portion 1.

As hereinabove described, the golf club according to the presentinvention is devised to keep the metal flow lines 3 effective to themaximum over the neck portion 2 and the face portion 1. The metal flowlines 3 continue not only in the neck portion 2 and the face portion 1but also on the surfaces thereof Thus, the hardness of the face portion1 can be homogenized while relatively highly keeping the hardness of theneck portion 2 and the face portion 1 as described above.

A method of manufacturing a golf club according to the present inventionand a sectional structure of a material in each step are now describedwith reference to FIGS. 8 to 19.

First, a rod member 5 consisting of carbon steel or the like subjectedto drawing plastic working for reducing the sectional area of a firstend is prepared as shown in FIG. 8. This drawing plastic working can beperformed by rolling the first end of the rod member 5 with a roll, forexample. At this time, attention is so given that metal flow lines 3 ofthe rod member 5 shown in FIG. 14 are not discontinuous.

The density of the metal flow lines 3 on the first end of the rod member5 can be improved as shown in FIG. 15 by performing drawing plasticworking on the first end of the rod member 5 in the aforementionedmanner. A neck portion 2 is formed on the first end while a face portion1 is formed on a second end. Therefore, it is inferable that the densityof the metal flow lines 3 on the neck portion 2 is higher than thedensity of the metal flow lines 3 on the face portion 1.

Processing other than the aforementioned rolling can be employed ifcapable of plastically working the first end of the rod member 5 andreducing the sectional area of the rod member 5.

Then, the rod member 5 is bent as shown in FIGS. 9 and 16. Thereafterrough forging is performed in three stages, as shown in FIG. 10A and 10Bto 12A and 12B. This rough forging is performed in a mold with a hammerof 1 ton.

As shown in FIGS. 17 to 19, substantially complete metal flow lines 3can be ensured in the material by plastically working the rod member 5stepwise. More specifically, it is possible to render the metal flowlines 3 continuously extend from the neck portion 2 toward the faceportion 1 while rendering these metal flow lines 3 extended along thestroking surface in a layered manner on the face portion 1.

As shown in FIGS. 12A and 12B, the rod member 5 can be deformed into ashape close to a final shape due to this rough forging in three stages,whereby a final golf club head can be formed by performing onlyprecision forging described later. Therefore, no machining may be addedin a final stage but the metal flow lines 3 can be prevented frompartial cutting.

Then, trimming is performed followed by precision forging as finalfinishing for forming portions such as scoring lines, as shown in FIGS.13A and 13B. It follows that a golf club head comprising the faceportion 1 and the neck portion 2 integrally formed while ensuringsubstantially complete metal flow lines 3 is obtained through theaforementioned steps. A golf club is manufactured with this golf clubhead.

Although the above embodiment has been described with reference to thecase of applying the present invention to an iron club, the idea of thepresent invention is also applicable to a face for a wood club. The facefor a wood club can be manufactured by forging a material properlyadjusted in diameter and length, for example.

Although the embodiment of the present invention has been illustrated asdescribed above, the embodiment disclosed this time is to be consideredillustrative in all points and not restrictive. The scope of the presentinvention is shown by the scope of claim for patent, and it is intendedthat all modifications within the meaning and range equivalent to thescope of claim for patent are included.

INDUSTRIAL AVAILABILITY

The present invention can be effectively applied to a golf club.

What is claimed is:
 1. A golf club comprising: a face portion (1) havinga stroking surface; and a neck portion (2) connecting said face portion(1) with a shaft, wherein metal flow lines (3) continue from said neckportion to said face portion (1), and wherein the difference between themaximum value and the minimum value of Vickers hardness (Hv) on astroking portion of said face portion (1) is not more than
 30. 2. Thegolf club according to claim 1, wherein a majority of said metal flowlines (3) extend in a single direction in sad face portion.
 3. The golfclub according to claim 2, wherein a majority of said metal flow lines(3) extend along a plane parallel to said stroking surface.
 4. The golfclub according to claim 1, wherein a majority of said metal flow lines(3) extend along a direction from said neck portion (2) toward a toe (4)of said face portion (1).
 5. The golf club according to claim 1, whereinthe Vickers hardness on said stroking portion is at least 130 and notmore than
 160. 6. The golf club according to claim 1, wherein tieVickers hardness on said stroking portion is at least 140 and not morethan
 160. 7. A Method of manufacturing a golf club comprising the stepsof: bending a rod member (5) reduced in sectional area by drawingplastic working; and forging said rod member (5) after said bending forintegrally forming a face portion (1) and a neck portion (2); whereinsaid drawing plastic working is performed to plastically work a firstend of said rod member (5) to be smaller in sectional area than a secondend while increasing metal flow line density on said first end of saidrod member (5); and wherein the difference between the maximum value andthe minimum value of Vickers hardness (Hv) on a stroking portion of saidface portion (1) is not more than
 30. 8. The method of manufacturing agolf club according to claim 7, wherein said forging step includes: afirst forging step of performing rough forging on said rod member (5) aplurality of times for approximating the shape of said rod member (5) toa final shape while ensuring metal flow lines (3); and a second forgingstep of performing precision forging on a material obtained after saidrough forging for working said material into said final shape.
 9. Themethod of manufacturing a golf club according to claim 7, forming saidneck portion (2) on a first end of said rod member (5) subjected to saiddrawing plastic working, and forming said face portion (1) on a secondend of said rod member (5).
 10. A method of manufacturing a golf clubcomprising the steps of: providing a face portion (1) having a strokingsurface; and providing a neck portion (2) connecting said face portion(1) with a shaft; wherein metal flow lines (3) continue from said neckportion to said face portion (1); and wherein the difference between themaximum value and the minimum value of Vickers hardness (Hv) on astroking portion of said face portion (1) is not more than
 30. 11. Themethod according to claim 10, wherein a majority of said metal flowlines (3) extend in a single direction in said face portion.
 12. Themethod according to claim 10, wherein a majority of said metal flowlines (3) extend along a plane parallel to said stroking surface. 13.The method according to claim 10, wherein a majority of said metal flowlines (3) extend along a direction from said neck portion (2) toward atoe (4) of said face portion (1).
 14. The method according to claim 10,wherein the Vickers hardness on said stroking portion is at least 130and not more than
 160. 15. The method according to claim 10, wherein theVickers hardness on said stroking portion is at least 140 and not morethan 160.